diff --git a/web-server/plugins/slycat-cca/js/new-ui.js b/web-server/plugins/slycat-cca/js/new-ui.js
index eade25ce8..02a320b1f 100644
--- a/web-server/plugins/slycat-cca/js/new-ui.js
+++ b/web-server/plugins/slycat-cca/js/new-ui.js
@@ -161,8 +161,11 @@ define(["slycat-server-root", "slycat-web-client", "slycat-dialog", "knockout",
       if( input_columns.length > component.row_count() || output_columns.length > component.row_count() )
       {
         dialog.dialog({
-          message:"The number of outputs and inputs must be less than or equal to " + component.row_count() + ", because that is the number of rows in the data."
-        })();
+          message:"The number of outputs and inputs must be less than or equal to " + component.row_count() + 
+                  ", because that is the number of rows in the data. You have selected " + input_columns.length +
+                  " inputs and " + output_columns.length + " outputs."
+
+        });
       }
       else
       {
diff --git a/web-server/plugins/slycat-cca/js/rerun-ui.js b/web-server/plugins/slycat-cca/js/rerun-ui.js
index 161033572..4510105a3 100644
--- a/web-server/plugins/slycat-cca/js/rerun-ui.js
+++ b/web-server/plugins/slycat-cca/js/rerun-ui.js
@@ -15,6 +15,7 @@ define(["slycat-server-root", "slycat-web-client", "slycat-dialog", "knockout",
     });
     component.attributes = mapping.fromJS([]);
     component.scale_inputs = ko.observable(false);
+    component.row_count = ko.observable(null);
 
     client.get_model_arrayset_metadata({
       mid: component.original._id(),
@@ -22,7 +23,7 @@ define(["slycat-server-root", "slycat-web-client", "slycat-dialog", "knockout",
       arrays: "0",
       statistics: "0/...",
       success: function(metadata) {
-        console.log(metadata);
+        component.row_count(metadata.arrays[0].shape[0]); // Set number of rows
         var attributes = [];
         for(var i = 0; i != metadata.arrays[0].attributes.length; ++i)
         {
@@ -126,44 +127,56 @@ define(["slycat-server-root", "slycat-web-client", "slycat-dialog", "knockout",
           output_columns.push(i);
       }
 
-      client.put_model_parameter(
+      if( input_columns.length > component.row_count() || output_columns.length > component.row_count() )
       {
-        mid: component.model._id(),
-        aid: "input-columns",
-        value: input_columns,
-        input: true,
-        success: function()
+        dialog.dialog({
+          message:"The number of outputs and inputs must be less than or equal to " + component.row_count() + 
+                  ", because that is the number of rows in the data. You have selected " + input_columns.length +
+                  " inputs and " + output_columns.length + " outputs."
+
+        });
+      }
+      else
+      {
+        client.put_model_parameter(
         {
-          client.put_model_parameter(
+          mid: component.model._id(),
+          aid: "input-columns",
+          value: input_columns,
+          input: true,
+          success: function()
           {
-            mid: component.model._id(),
-            aid: "output-columns",
-            value: output_columns,
-            input: true,
-            success: function()
+            client.put_model_parameter(
             {
-              client.put_model_parameter(
+              mid: component.model._id(),
+              aid: "output-columns",
+              value: output_columns,
+              input: true,
+              success: function()
               {
-                mid: component.model._id(),
-                aid: "scale-inputs",
-                value: component.scale_inputs(),
-                input: true,
-                success: function()
+                client.put_model_parameter(
                 {
-                  client.post_model_finish(
+                  mid: component.model._id(),
+                  aid: "scale-inputs",
+                  value: component.scale_inputs(),
+                  input: true,
+                  success: function()
                   {
-                    mid: component.model._id(),
-                    success: function()
+                    client.post_model_finish(
                     {
-                      component.tab(2);
-                    }
-                  });
-                }
-              });
-            }
-          });
-        }
-      });
+                      mid: component.model._id(),
+                      success: function()
+                      {
+                        component.tab(2);
+                      }
+                    });
+                  }
+                });
+              }
+            });
+          }
+        });
+      }
     }
 
     return component;